The present invention relates generally to communications, and more particularly to systems for communications internally and in close proximity to vehicles having metallic structures. The invention is particularly useful at radio frequencies in the range of 0.1 to 100 MHz, with some variants of the invention able to operate at ranges above 500 MHz.
It is desirable to communicate information between various locations within and around vehicles, including but not limited to cars, trucks and tractor-trailers, trains, ships and planes. Traditionally, this has been obtained by installing conductive wires between points. More recently, optical cable has somewhat similarly been employed in this role. Traditional wireless technologies in the 2.4 and 5 GHz frequency bands are also used.
Unfortunately all of these prior art systems have disadvantages. Wire and optical cable consume appreciable material and require routing between the various locations using the information, often entailing considerable design complexity. The conventional wireless technologies also often entail considerable design complexity, both to ensure that the integrity of the information is maintained against corrupting influence from outside the vehicle as well as to ensure that the energy being used to communicate the information does not become a corrupting influence on other systems.
These concerns are exacerbated in the context of vehicles. Firstly, a vehicle has particular structure. It has compartments, that is, spaces or cavities. These include large compartments, which are here termed xe2x80x9cmajor compartments.xe2x80x9d For example and without limitation, in a common automobile the major compartments are the engine or under-hood compartment, the passenger compartment, and the trunk or boot. In a common freight-hauling truck the major compartments are the engine compartment, driver/passenger compartment, and the cargo area. In common vehicles the glove box or other interior storage areas, for instance, are not major compartments. As a generalization, physical access to the major compartments of a vehicle is usually available. In contrast, physical access to the other compartments of a vehicle often is problematical.
Secondly, a vehicle is mobile by its very nature. Its systems therefore have the ability to be corruptingly influenced or to become a corrupting influence in highly varying and very difficult to predict manners. For an example, consider the traditional wireless technologies in the 2.4 or 5 GHz frequency bands. If a vehicle employing these is brought near sensitive electronic equipment it may cause disruption of that equipment. Conversely, the very same vehicle may itself be severely disrupted if brought near high powered electronic equipment. These concerns complicate information communication within (which we will regard here as including attached to the outside of) and in close proximity to vehicles.
Accordingly, what is needed are better systems for communications within and near to vehicles. Such systems should preferably have the capability for a single transmission to reach all of the vehicle compartments, as well as the near proximity outside the vehicle, without the use of repeaters or multiple physical access points.
Accordingly, it is an object of the present invention to provide an exciter system and excitation methods for communications within and very near to vehicles.
Briefly, one preferred embodiment of the present invention is a system for communicating information between a first location within a vehicle and a second location either within or very near to the vehicle. The vehicle has a conductive metallic structure defining one or more major compartments. An exciter unit is provided that includes a first communication equipment and an exciter device that is conductively connected to the metallic structure of the vehicle. A remote unit is also provided that includes a second communication equipment having a probe that is not conductively connected to the metallic structure of the vehicle. The first communication equipment may accept the information at the first location and modulate a signal with it. The signal has a carrier frequency that exhibits cut-off at one half-wavelength, as defined by the smallest dimension of the major compartments of the vehicle. Operation at frequencies below cut-off produces evanescent electromagnetic fields. Operation at frequencies above cut-off produces the more conventional propagating electromagnetic fields. The exciter device can then receive the signal from the first communication equipment and conductively inject it as a current into the metallic structure of the vehicle such that an electromagnetic field is produced. The second communication equipment then is able to couplingly receive the electromagnetic field from the metallic structure of the vehicle via the probe, demodulate the information from the electromagnetic field, and provide the information at the second location. The second communication equipment also may accept the information at the second location, modulate the electromagnetic field with it, and couplingly transmit the electromagnetic field into the metallic structure of the vehicle via the probe, such that the current is generated there in. The exciter device then may conductively extract the signal, as the current, from the metallic structure of the vehicle and provide it to the first communication equipment. The first communication equipment is then able to demodulate the information from the signal and provide it at the first location. This accordingly provides the ability to communicate the information between the first location and the second location in a wireless manner.
Briefly, another preferred embodiment of the present invention is a system for communicating information between at least two locations within a vehicle. The vehicle has a conductive metallic structure defining one or more major compartments. A number of exciter units are provided, equaling the number of the locations and each including a communication equipment and an exciter device that is conductively connected to the metallic structure of the vehicle. The communication equipment may each accept the information at its respective location and modulate a signal with it, wherein the signal alternates at a radio frequency. The exciter devices may then receive the signal from their respective communication equipment and conductively inject it as a current into the metallic structure of the vehicle. The exciter devices may each also conductively extract the current from the metallic structure of the vehicle, obtain the signal from the current, and provide the signal to its respective communication equipment. The communication equipment may then demodulate the information from the signal and provide it at its respective location. This accordingly provides the ability to communicate the information between the locations in a wired equivalent manner.
An advantage of the present invention for wireless vehicle communications is that the dimensions of vehicles, particularly for the major compartments within a vehicle, are generally small with respect to the radio frequency (RF) wavelengths for proposed operations. This results in reduced transmission path losses thereby reducing the communications transmitter power required. Another aspect of the small vehicle interior dimensions with respect to operating wavelengths is that the dominant electromagnetic field within the vehicle will be evanescent fields generated by the exciter injected RF currents in the vehicle""s metallic structure. Evanescent fields do not propagate and thereby do not introduce blockage or multipath effects within the vehicle, effects common to conventional propagation systems.
Another advantage of the invention for wireless vehicle communications is that at frequencies above cutoff, where cutoff occurs when the wavelength equals xc2xd the smallest dimension of the major compartments of the vehicle, the invention continues to inject currents in the structure and also supports more conventional electromagnetic waves fields that may also be used for wireless communications.
Another advantage of the invention for wireless vehicle communications is that the RF currents flow to all the interconnected metallic structures of the vehicle. These currents then cause electromagnetic fields in all compartments of the vehicle, particularly including the major compartments, thereby enabling wireless communications between the exciter and remote devices and probes located within these compartments.
Another advantage of the invention for wireless vehicle communications is that the electromagnetic field leakage to the near proximity of the outer surfaces of the vehicle enables communications between the exciter and remote devices and probes located near the external surface of the vehicle.
Another advantage of the invention for wireless vehicle communications is that the exciter has sufficient usable, controllable bandwidth that it can be used to establish numerous communications links, data buses or network applications without interference between the various communications applications.
Another advantage of the invention for wireless vehicle communications is that it can provide contiguous bandwidth across a wide range. This can include 0.1 MHz to the cutoff frequency for evanescent fields and additional contiguous bandwidth from the cutoff to and above 100 MHz for propagating waves.
Another advantage of the invention for wireless vehicle communications is that it uses the size of a vehicle structure to eliminate the need for very large antennas.
And another advantage of the invention for wireless vehicle communications is that low power remote unit xe2x80x9cprobesxe2x80x9d can be used to couple with the conductive framework of the vehicle in order to transmit signals back to the exciter, with the unique relationship of the exciter system to the conductive framework allowing reception of such weak signals.
An advantage of the invention for wired equivalent vehicle communications is that the dimensions of vehicles are generally small with respect to the RF wavelengths for proposed operations. This results in reduced transmission path losses thereby reducing the communications transmitter power required.
Another advantage of the invention for wired equivalent vehicle communications is that the RF currents flow to all the interconnected metallic structures of the vehicle. These currents can then be received at any point in or on the vehicle metallic structure thereby enabling communications between exciters at points on the inside and outside of the metallic structure of the vehicle.
Another advantage of the invention for wired equivalent vehicle communications is that communications between exciters within or on a vehicle, utilizing the metallic structure of the vehicle, reduces the level of interference from external sources or by internal interference sources of the vehicle such as the ignition, electric window operation or other electrical interference sources. This is accomplished because all antenna-like elements and wires are eliminated in a wired equivalent communication application and the invention need only operate in the reduced environment of return ground currents in the very low impedance of the metallic structure.
And another advantage of the invention for wired equivalent vehicle communications is that it can provide contiguous bandwidth from 0.1 MHz to greater than 100 MHz. Furthermore, the directly connected exciters can inject currents in the vehicle metallic structure at frequencies to and above 500 MHz and thereby establish propagating electromagnetic fields external to the vehicle. This feature permits communications links to and from the vehicle in frequency bands where regulatory allocations for specific applications currently exist. Examples are the 315 and 433 MHz bands for vehicle remote keyless entry and garage door openers.
An advantage of the invention for both wireless and wired equivalent vehicle communications is that the exciter has sufficient usable, controllable bandwidth that it can be used to establish numerous communications link, data bus or network applications without interference between the various communications applications.
Another advantage of the invention for both wireless and wired equivalent vehicle communications is that the exciter component can serve multiple functions and eliminate the need for separate antenna-like components.
And another advantage of the invention for both wireless and wired equivalent vehicle communications is that the exciter component is physically compact in structure and can be installed and become operational very quickly.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings.